Method of making wide flat sheets



Dec. 4, 1962 J. J. HEGER METHOD o3 MAKING WIDE FLAT SHEETS Filed June 18, 1958 lNl/E/V TOR JAMES J. HEGER By )dML A/fOf/IQ) United States Patent 3,066,384 METHOD OF MAKING WtDE FLAT SHEETS James J. Heger, Bethel Park, Pa., assignor to United States Steel Corporation, a corporation of New Jersey Filed June 18, 1958, Ser. No. 742,764 2 Claims. (Cl. 29-19) This invention relates to the rolling of metal sheets and, in particular, to the manufacture of exceptionally wide sheets of ferrous and non-ferrous metals ordinarily difficult to roll, having a flatness within very narrow limits. Both ferrous and non-ferrous metals have been pro duced in the form of thin sheets having a good surface and high degree of flatness. The maximum width which it is possible to make on modern cold-rolling mills is about 80". Certain metals and alloys however, cannot be successfully cold-rolled and must be reduced to final gage by hot-rolling. It is desirable, furthermore, to produce thin sheets of these metals and alloys difficult to roll (some of which can be hot-rolled to a maximum Width of only about 36") in widths greater than that of the widest sheet ordinarily made by cold-rolling. Plates have been produced in such widths by hot-rolling on mills having a nominal capacity up to 160" but it is not possible to produce thin sheets, e.g., sheets .033" thick, of great widths and a high degree of flatness by the plate-rolling technique.

I have invented a novel method for producing exceptionally wide thin sheets of metals which are difficult to roll, having a high degree of flatness. My method is an improvement on the practice disclosed in Orr Patent No. 2,645,842 and utilizes the basic concept of sandwich rolling disclosed therein. In a preferred practice of the invention, briefly described, I assemble a pack of plates of the metal difficult to roll with a weld-preventing medium therebetween. I place the pack in a box welded from carbon-steel top and bottom plates and side and end bars, with weld-preventing medium between the pack and box walls. After heating the resulting composite slab to rolling temperature, I roll it in a plate mill to effect the desired reduction of the plates forming the pack. When the rolling has been finished and the slab has cooled, I subject it to a thermal treatment such as refrigeration, annealing, austenitizing, age-hardening or quenching and tempering, while the pack is still enclosed in the box. On completion of such treatment, I then shear off the side and end bars and separate the resulting sheets.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawings illus trating the present preferred embodiment. In the drawmgs:

FIGURE 1 is a perspective view showing the assembled composite slab;

FIGURE 2 is a diagrammatic sketch showing the rolling of the slab; and

FIGURE 3 is a partial section through the finished pack.

In the following detailed description, the metal which is diflicult to roll will be designated special metal. Examples are stainless steel, other ferrous alloys, non-ferrous metals such as titanium, zirconium and their alloys. When steel is mentioned without qualification, carbon steel is to be understood. I produce plates of special metal such as l8-8 stainless steel, thick or thereabouts and, roughly, 38" wide by 48" long. I assemble these plates, shown at 10 in FIGURE 1, into a pack of three to six or eight thicknesses after coating the top of each plate with a weld preventive such as a water slurry of magnesium and chromium oxides.

The pack of plates 10 is placed in a box 11 welded from a steel bottom plate 12 and side and end bars 13. The

bars are about 2" thick. Plates I2 are about 1" thick and overhang plates 10 by 2 to 6" in each direction. A weld preventive is applied to the bottom of the pack before it is placed in the box. Each bar 13 has vent holes 14 drilled therethrough. After placing the pack of plates 10 in box 11, cover plate 15 is welded onto the latter. The resulting composite slab 16 is then placed in a furnace and heated to rolling temperature, e.g., 2200 F. As shown, plates 12 and 15 overlap bars 13 so the welds are not engaged by the rolls during the reduction now to be described.

The heated slab (about 50 x 60") is rolled as shown in FIGURE 2. Slab 16 is first rolled sidewise in the direction of its width W, known as cross rolling, in a mill 17, until elongated to about 60" x This rolling will require several passes back and forth through the mill which is of the reversing type. The resulting breakdown 18 is then similarly rolled in the direction of its original length L, in a mill 19, to produce an encased pack of sheets Ztl of finished dimensions, say 100 x 250". Both the cross rolling and the finish rolling may be effected in mill 19 simply by turning the breakdown 90 after cross rolling. After completion of the rolling, the pack is per mitted to cool somewhat. It is given a roller leveling while still at a temperature between 400 and 1600 F., preferably about 900 F. The widening and elongation of the starting slab result in the formation of sheets of special metal 90 x 230 and about .033 thick. Plates 12 and 15 have been correspondingly reduced and bars 13 converted to the form of plates.

After rolling and while the pack retains its integrity, I subject it to a thermal treatment to impart to the sheets of special metal the desired physical properties. The thermal treatment may be refrigeration, annealing, age hardening, autenitizing, quenching and tempering or any combination thereof. For example, the pack is normalized for a half-hour at 1850 F., air cooled and then tempered for four hours at 800 F. The following are further typical heat-treatments which I may employ:

(1) Solution anneal or autenitize in the range 1500 F. to 2200 F. for fifteen minutes to eight hours; cool in air, oil, water or brine; reheat in the range 200 F. to 1500 F. for fifteen minutes to one hundred hours; cool in air, oil, water or brine.

(2) Heat in the range 200 to 1700 F. for fifteen minuters to one hundred hours; cool in a furnace, air, oil, water or brine or in accordance with a predetermined cycle as may be desired to achieve the desired properties.

(3) Refrigerate in the range 0 to -200 F. for fifteen minutes to one hundred hours; heat for fifteen minutes to one hundred hours in the range of 200 F. to 1750 F.; cool in furnace, air, oil, water or brine or in accordance with any predetermined cycle deemed necessary to achieve the desired properties.

After the pack has been thermally treated to obtain the desired physical properties, it is flattened by roller leveling or stretcher leveling. The plates to Which side and end bars 12 and 15 have been reduced are sheared from plates 12 and 15 enclosing the pack and the latter is opened by separating the sheets thereof. These sheets will be found to have a good surface, uniform thickness and a high degree of flatness. This latter results principally from carrying out the thermal treatment while the sheets are still enclosed in the box, which avoids warping, curling or buckling.

Although I have disclosed herein the preferred embodiment of my invention, I intend to cover as Well any change or modification therein which may be made without departing from the spirit and scope of the invention.

I claim:

1. A method of makingfrom 80" wide to wide thin sheets of a metal which is difficult to roll selected from the group consisting of stainless steel, ferrous alloys, titanium, zirconium and their alloys, which consists in assembling a pack of plates of said metal with weld-preventing material therebetween, placing the pack within a box welded up from steel top and bottom plates and steel side and end bars with the top and bottom plates overlapping the side and end bars, providing vent holes in all said bars, hot rolling the resulting pack-in-a-box first by cross rolling and then by rolling longitudinally, thereby reducing the first-mentioned plates to sheets, then subjecting said sheets while still confined within said box to heating and cooling stages in predetermined order thereby developing desired physical properties in said sheets, roller leveling the hot-rolled pack while still in the box, and then opening said box and removing and separating said sheets.

2. A method of making from 80" wide to 160" wide thin sheets of a metal which is difficult to roll selected from the group consisting of stainless steel, ferrous alloys, titanium, zirconium and their alloys, which consists in assembling a pack of plates of said metal with weld-preventing material therebetween, placing the pack Within a box welded up from steel top and bottom plates and steel side and end bars with the top and bottom plates overlapping the side and end bars, providing vent holes in all said bars, hot rolling the resulting pack-in-a-box first by cross rolling and then by rolling longitudinally, thereby reducing the first-mentioned plates to sheets, roller-leveling the pack while still in the box, then subjecting said sheets while still confined within said box to heating and cooling stages in predetermined order thereby developing desired physical properties in said sheets, roller leveling the hot-rolled pack while still in the box, and then opening said box and removing and separating said sheets.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Project Rand, pub. March 15, 1959 by the Rand Corp. 1500 4th St., Santa Monica, Calif., pages 1920.

Metals Technology, February 1946, pub. by the American Institute of Mining and Metallurgical Engineers Inc. 29 39th St., New York 18, N.Y., vol. 13, No. 2, article on Ductile Titanium, pages 10-15. 

